Japanese bank Nomura has penned a report flagging concerns over the recent “fixation” on a fund's active share, warning that it could distort the European Securities and Markets Authority’s probe into the extent of closet indexing.

The European focus on closet indexers - fund managers which charge active fees while effectively tracking the index - has sharpened in recent months. In November Esma confirmed it was on a fact-finding mission to "assess the scope of this issue".